n-type Mg2(Si0.4Sn0.6)1-xSbx compounds were synthesized using high-pressure techniques followed by spark plasma sintering. Structural and compositional analyses revealed a predominant anti-fluorite ...phase with minimized oxidation and volatilization of Mg, leading to improved thermoelectric properties in our samples. This study highlights the controllable nature of composition, distribution, and fraction of in-situ nanostructures through specific high-pressure synthesis conditions and spark plasma sintering. X-ray diffraction, backscattered images, and Scanning transmission electron microscopy results showed that the nanoprecipitates consist of a solid solution phase of Mg2Sn and Mg2Si with varying compositions. The Mg2(Si0.4Sn0.6)0.98Sb0.02 sample has the lowest lattice thermal conductivity, 1.14 Wm−1K−1 at room temperature and 0.53 Wm−1K−1 at 623 K. The optimal Mg2(Si0.4Sn0.6)0.98Sb0.015 composition demonstrated the highest power factor and lowest thermal conductivity, resulting in a peak ZT value of 1.48 at 823 K. The decrease in thermal conductivity, along with a thorough comprehension of the microstructural elements responsible for this decrease, can offer valuable insights and guidance for advancing thermoelectric materials with a high thermoelectric figure of merit. Our findings highlight the benefits of utilizing high pressure in the synthesis of Mg2Si-based thermoelectric materials to improve their thermoelectric performance.
•Mg2 (Si0.4 Sn0.6)1-xSbx was synthesized with high pressure synthesis.•HPS effectively eliminates the oxidation and volatilization of Mg.•A low lattice thermal conductivit of 0.53Wm−1k−1 in Mg2 (Si0.4 Sn0.6) 0.98Sb0.02 at 623 K.•The highest ZT of 1.48 was achieved in the optimal sample Mg2 (Si0.6 Sn0.4)0.985Sb0.015 at 823 K
A series of n-type Mg2(Si0.3Sn0.7)1-xBix compounds with 0≤x≤0.02 were successfully synthesized through a combined approach involving solid-state reaction, high-pressure synthesis, and spark plasma ...sintering techniques. The method yielded homogeneously distributed single-phase materials at the micron scale, although minor compositional variations were detected within nanoscale precipitates embedded in the grains. The sample with Bi content of 0.01 exhibited enhanced thermoelectric properties, reaching a peak thermoelectric figure of merit (ZT) of 1.45 at 700 K while maintaining an average ZT of about 1.1 over the temperature range of 300−773 K. The enhancement in thermoelectric performance is ascribed to the optimized carrier concentration, band convergence, and refined microstructure. The findings suggest a simplified approach to doping that could be beneficial in creating high-performance thermoelectric materials for energy conversion.
•Successfully fabricated Mg2(Si0.3Sn0.7)1-xBix bulks via solid-state reaction, high-pressure and spark plasma sintering.•The samples are homogeneous at the micrometer scale and slight compositional fluctuations at nanoscale.•The ZTmax of 1.45 at 700 K and ZTave of about 1.1 (300‐773 K) was achieved in optimal Mg2(Si0.3Sn0.7)0.99Bi0.01.•The high-pressure synthesis process is an effective strategy for doping.
The building blocks that form the complex structures of the new phosphorus oxide nitrides P40O31N46 and P74O59N84 can be intergrown with further compounds. They are comparable to silicates in the ...Earth's crust, which is symbolized by a cutout of the disordered crystal structure. The background shows a typical diffraction pattern acquired with microfocused synchrotron radiation as used for the structure elucidation. More information can be found in the Research Article by W. Schnick, O. Oeckler and co‐workers (DOI: 10.1002/chem.202203892).
Half metals, in which one spin channel is conducting while the other is insulating with an energy gap, are theoretically considered to comprise 100% spin‐polarized conducting electrons, and thus have ...promising applications in high‐efficiency magnetic sensors, computer memory, magnetic recording, and so on. However, for practical applications, a high Curie temperature combined with a wide spin energy gap and large magnetization is required. Realizing such a high‐performance combination is a key challenge. Herein, a novel A‐ and B‐site ordered quadruple perovskite oxide LaCu3Fe2Re2O12 with the charge format of Cu2+/Fe3+/Re4.5+ is reported. The strong Cu2+(↑)Fe3+(↑)Re4.5+(↓) spin interactions lead to a ferrimagnetic Curie temperature as high as 710 K, which is the reported record in perovskite‐type half metals thus far. The saturated magnetic moment determined at 300 K is 7.0 μB f.u.−1 and further increases to 8.0 μB f.u.−1 at 2 K. First‐principles calculations reveal a half‐metallic nature with a spin‐down conducting band while a spin‐up insulating band with a large energy gap up to 2.27 eV. The currently unprecedented realization of record Curie temperature coupling with the wide energy gap and large moment in LaCu3Fe2Re2O12 opens a way for potential applications in advanced spintronic devices at/above room temperature.
Half metals have promising applications in advanced spintronic devices. A new half metal LaCu3Fe2Re2O12 with a record‐high Curie temperature (TC) in perovskite oxides, combining with a wide spin‐up energy gap (Eg) and a large magnetization (MN), is synthesized. The current LaCu3Fe2Re2O12 thus shows the best synthetic performance (TC × Eg × MN) among all half‐metallic oxides discovered so far.
The layered honeycomb lattice material α‐RuCl3 has emerged as a prime candidate for displaying the Kitaev quantum spin liquid state, and as such has attracted much research interest. Here a new ...layered honeycomb lattice polymorph of RuI3, a material that is strongly chemically and structurally related to α‐RuCl3 is described. The material is synthesized at moderately elevated pressures and is stable under ambient conditions. Preliminary characterization reveals that it is a metallic conductor, with the absence of long‐range magnetic order down to 0.35 K and an unusually large T‐linear contribution to the heat capacity. It is proposed that this phase, with a layered honeycomb lattice and strong spin–orbit coupling, provides a new route for the characterization of quantum materials.
Honeycomb‐layer‐structure RuI3 is synthesized at moderately high pressures. Preliminary characterization reveals metallic, paramagnetic behavior with no long‐range magnetic order down to 0.35 K, and an unusually large T‐linear contribution to the heat capacity. This RuI3 phase with a layered honeycomb lattice and strong spin–orbit‐coupling, may provide a new route for the characterization of quantum materials.
Novel ternary nitride semiconductor MgSnN2 was synthesized using the metathesis reaction under high pressure (P = 5.5 GPa/T = 850 °C/1 h). MgSnN2 obtained in this study showed a rocksalt structure, ...although we have reported that ZnSnN2 synthesized using a similar method has a wurtzite structure. The (111) plane of MgSnN2 with a rocksalt structure is expected to match well with GaN (0001). The band gap of MgSnN2 is estimated to be 2.3 eV and it shows a distinct cathodoluminescence peak at room temperature. MgSnN2 can find potential use in photovoltaic absorber, in the emitting layer of a light‐emitting device, and photocatalyst or opaque pigment because the elements composing MgSnN2 are nontoxic and earth‐abundant. MgSnN2 powder synthesized in this study showed excellent crystallinity, proving that metathesis reaction under high pressure is a superior method for synthesizing novel multicomponent nitrides.
A novel ternary nitride of MgSnN2 was synthesized using the high‐pressure metathesis reaction. The Rietveld refinement revealed that the structure of MgSnN2 has rocksalt‐structure (space group: Fm3m) with the lattice constant of a = 4.483 Å. The (111) plane of MgSnN2 matches perfectly with wz‐GaN (001), which implies that MgSnN2 has a potential for electronic devices with an optical gap of 2.3 eV.
Inspired by the functional properties of ion defect induction and charge compensation in defect engineering, these methods are expected to be an effective strategy to solve the constraints of ...Li4Ti5O12 (LTO) inherent conductivity and diffusion dynamics, and further improve battery rate performance. The oxygen vacancy (OV) content in LTO can be controlled quantitatively by high‐pressure induction using the high‐pressure and high‐temperature (HPHT) method. In addition, the relationship between the electrochemical properties and OV is further explored. The theoretical calculations indicate that the OV defects cause the electrons to delocalize into the conduction band of the LTO, and thus fundamentally improve the intrinsic conductivity. In particular, the high‐pressure quenching strategy of HPHT causes LTO to instantly produce crack holes with massive crystalline layers, which can be regarded as storage for the electrolyte to facilitate ion diffusion. The fabricated LTO anodes containing OVs compensate for the limitation of the poor rate performance with a capacity of 176 mAh g−1 at 20 C. Pressure‐induced OV defects not only open up a new perspective in the field of lithium‐ion batteries (LIBs), but also provide a certain degree of freedom for the functional design characteristics of defect engineering.
High‐pressure induced and quantitatively regulated oxygen vacancies compensate for the limitations of lithium titanate conductivity and kinetics. In addition, the self‐high‐pressure quenching strategy produces abundant grain boundaries, interfaces, and vacancies, causing pseudo‐capacitance effect to increase the capacity. Furthermore, the fracture structures are used as a storage of electrolyte to facilitate ion diffusion kinetics, thus improving the electrochemical performance.
•The nanobelts are composed of SnO2 NPs and attached to ZnO NPs on the surface.•The ZnO-SnO2 sensor shows enhanced properties to TEA under UV irradiation.•UV laser irradiation enhanced TEA sensing ...mechanism is discussed in detail.•A growth mechanism of nanobelt morphology and heterostructure are proposed.
ZnO-SnO2 heterojunction nanobelts with hollow interiors are successfully designed and synthesized using a facile two-step method. The as-synthesized ZnO-SnO2 heterojunction nanobelts are used for the detection of the highly toxic and pungent volatile organic compound triethylamine (TEA). The sensing properties of the as-fabricated sensor under ultraviolet (UV) laser illumination are carefully investigated and the results exhibit fast response/recovery times, good sensitivity and superior repeatability with regard to the TEA detection. Specifically, the ZnO-SnO2 sensor exhibits a faster response speed (1.8 s) and recovery speed (18 s) under UV illumination conditions. The UV laser enhanced sensing mechanism of the heterojunction nanobelts is also discussed.
Magnetoelectric multiferroics have received much attention in the past decade due to their interesting physics and promising multifunctional performance. For practical applications, simultaneous ...large ferroelectric polarization and strong magnetoelectric coupling are preferred. However, these two properties have not been found to be compatible in the single‐phase multiferroic materials discovered as yet. Here, it is shown that superior multiferroic properties exist in the A‐site ordered perovskite BiMn3Cr4O12 synthesized under high‐pressure and high‐temperature conditions. The compound experiences a ferroelectric phase transition ascribed to the 6s2 lone‐pair effects of Bi3+ at around 135 K, and a long‐range antiferromagnetic order related to the Cr3+ spins around 125 K, leading to the presence of a type‐I multiferroic phase with huge electric polarization. On further cooling to 48 K, a type‐II multiferroic phase induced by the special spin structure composed of both Mn‐ and Cr‐sublattices emerges, accompanied by considerable magnetoelectric coupling. BiMn3Cr4O12 thus provides a rare example of joint multiferroicity, where two different types of multiferroic phases develop subsequently so that both large polarization and significant magnetoelectric effect are achieved in a single‐phase multiferroic material.
The A‐sited ordered perovskite BiMn3Cr4O12 presents a rare example of single‐phase multiferroic systems where both type‐I and type‐II multiferroic phases coexist. In sharp contrast to previous findings, large electric polarization and strong magnetoelectric effect are compatible in the current BiMn3Cr4O12, providing a new pathway for generating advanced multiferroic materials and devices.
Nitrogen-rich transition-metal nitrides hold great promise to be the next-generation catalysts for clean and renewable energy applications. However, incorporation of nitrogen into the crystalline ...lattices of transition metals is thermodynamically unfavorable at atmospheric pressure; most of the known transition metal nitrides are nitrogen-deficient with molar ratios of N:metal less than a unity. In this work, we have formulated a high-pressure route for the synthesis of a nitrogen-rich molybdenum nitride through a solid-state ion-exchange reaction. The newly discovered nitride, 3R–MoN2, adopts a rhombohedral R3m structure, isotypic with MoS2. This new nitride exhibits catalytic activities that are three times more active than the traditional catalyst MoS2 for the hydrodesulfurization of dibenzothiophene and more than twice as high in the selectivity to hydrogenation. The nitride is also catalytically active in sour methanation of syngas with >80% CO and H2 conversion at 723 K. Our formulated route for the synthesis of 3R–MoN2 is at a moderate pressure of 3.5 GPa and, thus, is feasible for industrial-scale catalyst production.
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